Kiru,
Agree with ur comments.
Arrangement and certain ideas are heavily inspired. But I think it is a fundamental misnomer to think songs and ideas pop out of nothing or nowhere. I'm quoting MSV here "From one comes the other" (He said this in context of his revelation that "Poo Malayil Or Malligai" is heavily drawn from the first flute interlude of Naushad's song "Tu mera chand main teri chandani" RDB has done wonderful work by taking some phrases from other musicians and their songs. Raja has several examples like this.
Artists work on creation with certain base in their mind. Sometimes that heavily transpires and other times less. ARR is great examples of this. He has some heavy reference songs but rarely copies. I'm yet to see some art which has no precedence.
The difference with great artist is, when they take from somewhere, they have something more to say or add. Their unique take. Their unique approach. Whereas mortals they just take and have nothing more to add to it. Then it becomes just a copy/lift.
Which leads to my favorite line from Oscar Wilde "Talent borrows, Genius steal" !!